1. Field of the Invention
The present invention relates to a spindle apparatus for supporting and rotating a workpiece, particularly, wherein a spindle center can be displaced in the axial direction of a spindle.
2. Discussion of the Prior Art
A cylindrical grinder designed to grind a cylindrical workpiece or a cam grinder is generally constructed as shown in FIG. 1.
Specifically, a wheel head 102 and a table 103 are arranged on a bed 101 and are slidable along guides in vertical and lateral directions in the drawing, respectively. A wheel shaft 105 is supported on the wheel head 102 and is driven for rotation by a motor 106 through a belt-and-pulley mechanism 107. A pair of grinding wheels 104a and 104b are mounted to the wheel shaft 105.
A spindle head 110 is mounted on one end of the table 103. A workpiece spindle 109 is supported by the spindle head 110 and driven in rotation from a motor 108. The workpiece spindle 109 includes a chuck and a center 129. Mounted on the other end of the table 103 is a tailstock 113 including a tailstock spindle 112. The tailstock spindle 112 includes a center 111 in a face-to-face relation to the workpiece spindle 109.
A pair of workpiece stand-by stations 114a and 114b are located on the table 103 adjacent to front ends of the workpiece spindle 109 and the tailstock spindle 112. An instrument 115 is provided on the bed 101 to sense the axial or longitudinal position of a workpiece.
In the prior art, a workpiece shifter 150 is located on the table 103 between the workpiece spindle 109 and the tailstock spindle 112.
The tailstock spindle 112 or the center 111 is in its retreated position before abrasive action is initiated.
A workpiece W is loaded temporarily on the workpiece stand-by stations 115a and 115b by a loader or similar means. The workpiece W is thereafter moved toward the workpiece spindle 109 by the workpiece shifter 150 until one end of the workpiece W is brought into engagement with the center 129 of the workpiece spindle 109. The tailstock spindle 112 is then advanced so that the other end of the workpiece W is brought into engagement with the center 111.
The end of the workpiece adjacent to the workpiece spindle is gripped by the chuck of the workpiece spindle 109.
The wheel head 102 is advanced while the workpiece W is being rotated by the motor 108. The workpiece W is then abraded by the grinding wheels 104a and 104b which are rotated by the motor 106.
After abrasive or grinding action has been completed, the wheel head 102 is moved back or retreated, and the motor 108 is stopped.
The workpiece W is then released from the chuck, and the tailstock spindle 112 is moved to its retreated position. The workpiece W is thereafter moved to the workpiece stand-by stations 114a and 114b by the workpiece shifter 150 and moved away from the system by the loader.
In such a conventional grinder, loading and unloading of a workpiece requires the use of the workpiece shifter 150. A large workpiece shifter is thus necessary when a large workpiece is to be loaded and unloaded.
The workpiece W is displaced from the workpiece stand-by stations 114a and 114b toward the workpiece spindle 109 by the workpiece shifter 150. This results in an increase in the distance between one end of the workpiece W and the tailstock spindle 112. The tailstock spindle 112 must project more toward the workpiece spindle 109 or must be moved more toward the workpiece spindle 109 to support the other end of the workpiece W in proportion to the displacement of the workpiece W by the workpiece shifter 150. This impairs the rigidity of the tailstock spindle 112.
A further problem of the prior art is that it takes quite a time to support the workpiece since the workpiece shifter 150 must be used to load the workpiece, and the tailstock spindle 112 must be moved by an increased distance.